Pickup device for high voltage leads of ignition systems



C. J. PUDEWILL PICKUP DEVICE FOR HIGH VOLTAGE LEADS OF IGNITION SYSTEMS Filed Dec. 22 1961 Feb. 22, 1966 nun nun Q NW m MNVNI JLI E k mw a Q1 IN VEN TOR. I 1 z I BY W Km ATTORNEYS.

mil 2 Ni United States Patent Office 3,237,080 PICKUP DEVICE FOR HIGH VOLTAGE LEADS F IGNITION SYSTEMS Carl J. Pudewill, Chicago, Ill., assignor to Sun Electric Corporation, Chicago, Ill., a corporation of Delaware Filed Dec. 22, 1961, Ser. No. 161,622 4 Claims. (Cl. 3219) This invention relates to pickup device and more particularly to a pickup for use in the secondary or high voltage leads of an internal combustion engine ignition system to derive controlled pulses therefrom for the operation of test apparatus.

Current transformers connected in the secondary leads of engine ignition systems have heretofore been used to supply triggering or controlling pulses to electrical valves, such as vacuum tubes, transistors and the like, for various testing operations. These current transformers, as heretofore constructed, have produced erratic results particularly when used on ignition systems including magnetos which alternate positive and negative pulses.

It is accordingly an object of the present invention to provide a pickup device which may be used in connection with the secondary leads of any type ignition system to produce distinct, clean and sharp pulses.

Another object is to provide a pickup device in which all input pulses are rectified and filtered to produce controlling pulses of the same wave shapes and of the same polarity for properly and accurately triggering various types of test apparatus.

According to a feature of the invention, the pickup device includes a current transformer having a tuned primary winding connected in circuit in the secondary leads of the engine ignition system and a center tapped secondary winding, the opposite ends of which are connected through filtering and rectifying circuits to a test device to be controlled.

The above and other objects and features of the invention will be more readily apparent from the following description when read in connection with the accompanying drawing, in which the single figure is a circuit diagram of a pickup device embodying the invention.

The pickup device, as shown, is adapted to be connected in the secondary or high voltage leads of an engine ignition system of the type utilizing either a magneto or a coil. As shown in the drawing, the pickup is applied to an engine ignition system including a magneto 10 of conventional construction grounded at one side and connected at its other side to the wiper 11 of a conventional distributor, including a plurality of contacts 12 connected respectively to spark plugs of the enme. g While only one spark plug is shown, it will be understood that each of the contacts 12 is connected to a different spark plug in the usual manner.

The pickup comprises a current transformer indicated generally at 13 having a multiple turn primary winding 14 connected in series in the high voltage lead between one of the contacts 12 and the spark plug 2%). A capacitor 15 is connected in parallel with the winding 14, as shown, and is of a value to form therewith a parallel resonant circuit which is resonant at the frequency of the individual pulse wave fronts so that pulses from the magneto will pass freely through the primary winding 14 with a minimum of impedance.

The input pulses from the magneto and which traverse the primary winding 14 will have a wave form generally as indicated immediately above the transformer and marked input signal. It will be noted that each of these pulses comprises an initial very sharp pulse of high amplitude followed by a series of pulses of decreasing am- 3,237,080 Patented Feb. 22, 1966 plitude and that the polarity of succeeding pulse signals is reversed with respect to each other. Pulses supplied from a coil would have a similar configuration except that all pulses would be of the same polarity.

The transformer is completed by a secondary winding 16 which is center tapped at 17 with the center tap being connected to ground, as shown. The opposite ends of the secondary winding are connected through identical filtering and rectifying circuits each comprising a series resistor 18 followed by a shunt resistor 19 to ground which is in turn followed by a choke coil 21. Beyond the choke coils the outer leads are connected through capacitors 22 to ground and then interconnected through similarly poled rectifiers 23. An additional filter circuit comprising a series resistor 24 bypassed on each side thereof by a capacitor 25 receives the pulses passing the rectifiers and further filters them. The output pulses from the final filter circuit are supplied to the test apparatus to be controlled, such as a transistor, vacuum tube, or the like.

The filter circuits in the outer leads from the secondary winding 16 will filter the input signal as transmitted by the secondary Winding so that immediately prior to rectification the waves in the opposite leads will have the form illustrated immediately above the choke coils 21. It will be noted that the original pulses after being filtered by the resistors 18 and 19, the choke coils 21 and the capacitors 22 constitute single pulses corresponding in their spacing to the initial pulses of the input signal and of the same polarity as the initial pulses of the input signal. The decerasing alternating vibrations following the initial pulse are completely filtered out and the base of the initial pulse is widened slightly. After rectification, the pulses will have the wave form illustrated immediately above the rectifiers 23. It will be seen that the form of these pulses is the same as that of the pulses prior to rectification, except that now both of the pulses are of the same polarity. After further filtering by the filter elements 24 and 25, the pulses are somewhat broadened and slightly reduced in amplitude, as indicated by the pulses marked output pulses above the output connection of the pickup circuit.

It will therefore be seen that the pickup of the present invention is capable of receiving pulses of opposite or identical polarity and of transmitting all of the pulses to the output circuit. This is made possible by use of the center tapped secondary winding on the transformer in conjunction with the filtering and rectifying circuits. Furthermore, the filtering accomplished by the filtering circuits insures that the output signal will constitute clean separate pulses capable of firing vacuum tubes, transistors, or the like, in a test instrument with a high degree of reliability and accuracy.

While one embodiment of the invention has been shown and described herein, it will be understood that it is illustrative only and not to be taken as a definition of the scope of the invention, references being had for this purpose to the appended claims.

What is claimed is:

1. A pickup device for use with the high voltage leads of internal combustion engine ignition systems comprising a transformer having a primary connected in series in a high voltage lead and a secondary, a grounded center tap on the secondary, leads from the ends of the secondary each including a resistor, a choke coil and a rectiher in series, both rectifiers conducting in a direction away from the secondary and the leads being interconnected beyond the rectifiers, resistors connected from the leads between the resistors and choke coils therein to ground, and capacitors connected from the leads between the choke coils and rectifiers therein to ground.

2. A pickup device for use with the high voltage leads of internal combustion ignition systems comprising a transformer having a primary winding connected in series in a high voltage lead and a secondary winding, a capacitor connected 'in' parallel with the primary winding and defining therewith a resonant circuit which is resonant at the frequency of individual voltage pulse wave transmitted through the lead fronts, filtering means connected to the secondary of the transformer to filter out oscillations in voltage pulses transmitted by the lead thereby to leave relatively sharp voltage pulses corresponding in spacing to the spacing of the voltage wave fronts, and rectifier means connected to the filtering means to transmit the last named relatively sharp voltage pulses.

3. A pickup device for use with the high voltage leads of internal combustion ignition systems comprising a transformer having a primary winding connected in series in a high voltage lead and a secondary winding, a capacitor connected in parallel with the primary winding and defining therewith a resonant circuit which is resonant of the frequency of individual voltage pulse wave transmitted through the lead fronts, a center tap on the transformer secondary connected to ground, a filter circuit connected to each end of the transformer secondary to filter out oscillations in voltage pulses transmitted by the lead thereby to leave relatively sharp voltage pulses corresponding in spacing to the spacing of the voltage wave fronts, a rectifier connected to each of the filter circuits, the rectifiers being poled in the same direction and connected to a common output lead.

4. A pickup device for use with the high voltage leads of internal combustion ignition systems comprising a transformer having a primary winding connected in series in a high voltage lead and a secondary winding, a capacitor connected in parallel with the primary winding and defining therewith a resonant circuit which is resonant at the frequency of individual voltage pulse wave transmitted through the lead fronts, a center tap on the transformer secondary connected to ground, leads from the ends of the secondary each including a resistor, a choke coil and a rectifier in series, both rectifiers conducting in a direction away from the secondary and the leads being interconnected beyond the rectifiers, resistors connected from the leads between the resistors and choke coils to ground, and capacitors connectedvfrom the leads between the choke coils and rectifiers to ground, the resistors, choke coils and capacitors constituting filter circuits to filter out the oscillations and to widen the sharp voltage pulses.

References Cited by the Examiner UNITED STATES PATENTS 1,965,655 7/1934 Klotz et al. 321-10 2,084,904 6/1937 Geise 321-9 3,175,122 3/1965 Penn et al 315200 X FOREIGN PATENTS 1,081,126 3/1960 Germany.

770,896 3/ 1957 Great Britain.

LLOYD MCCOLLUM, Primary Examiner. 

1. A PICKUP DEVICE FOR USE WITH THE HIGH VOLTAGE LEADS OF INTERNAL COMBUSTION ENGINE IGNITION SYSTEMS COMPRISING A TRANSFORMER HAVING A PRIMARY CONNECTED IN SERIES IN A HIGH VOLTAGE LEAD AND A SECONDARY, A GROUNDED CENTER TAP ON THE SECONDARY, LEADS FROM THE ENDS OF THE SECONDARY EACH INCLUDING A RESISTOR, A CHOKE COIL AND A RECTIFIER IN SERIES, BOTH RECTIFIERS CONDUCTING IN A DIRECTION AWAY FROM THE SECONDARY AND THE LEADS BEING INTERCONNECTED BEYOND THE RECTIFIERS, RESISTORS CONNECTED FROM THE LEADS BETWEEN THE RESISTORS AND CHOKE COILS THEREIN TO GROUND, AND CAPACITORS CONNECTED FROM THE LEADS BETWEEN THE CHOKE COILS AND RECTIFIERS THEREIN TO GROUND. 